The Volume Retention directive defines the length of time that Susan will keep records associated with the Volume in the Catalog database after the End time of each Job written to the Volume. When this time period expires, and if AutoPrune is set to yes Susan may prune (remove) Job records that are older than the specified Volume Retention period if it is necessary to free up a Volume. Recycling will not occur until it is absolutely necessary to free up a volume (i.e. no other writable volume
exists). All File records associated with pruned Jobs are also pruned. The time may be specified as seconds, minutes, hours, days, weeks, months, quarters, or years. The Volume Retention is applied independently of the Job Retention and the File Retention periods defined in the Client resource. This means that all the retentions periods are applied in turn and that the shorter period is the one that effectively takes precedence. Note, that when the Volume Retention period has been reached, and
it is necessary to obtain a new volume, Susan will prune both the Job and the File records. This pruning could also occur during a status dir command because it uses similar algorithms for finding the next available Volume.

It is important to know that when the Volume Retention period expires, Susan does not automatically recycle a Volume. It attempts to keep the Volume data intact as long as possible before over writing the Volume.

By defining multiple Pools with different Volume Retention periods, you may effectively have a set of tapes that is recycled weekly, another Pool of tapes that is recycled monthly and so on. However, one must keep in mind that if your Volume Retention period is too short, it may prune the last valid Full backup, and hence until the next Full backup is done, you will not have a complete backup of your system, and in addition, the next Incremental or Differential backup will be promoted to a Full
backup. As a consequence, the minimum Volume Retention period should be at twice the interval of your Full backups. This means that if you do a Full backup once a month, the minimum Volume retention period should be two months.

The default Volume retention period is 365 days, and either the default or the value defined by this directive in the susan-dir.conf file is the default value used when a Volume is created. Once the volume is created, changing the value in the :file:`susan-dir.conf` file will not change what is stored for the Volume. To change the value for an existing Volume you must use the update command in the Console.

